Reliability assessment of soil liners

The use of reliability based design (RBD) is continually gaining acceptance in geotechnical engineering. However, there is a paucity of RBD methods that currently exist in practice for the assessment of soil liner systems. This thesis attempt to address deficiencies in the literature of reliability based design of soil liner systems.;In Chapter 3, a two-dimensional RFEM soil model is used to examine the influence of correlation length and hydraulic conductivity distributions on the probability of failure for a clay liner system. An analysis is also provided of the influence of correlation length on the required sampling of natural clayey deposits and clayey liner systems for target reliabilities in quality assurance programs. The correlation length, hydraulic conductivity variance, mean, and sample frequency of the clayey liner are varied in the simulations to achieve the two objectives of Chapter 3. It is shown that a "worst case" correlation length exists which will produce conservative estimates of probability of failure and required sample sizes for quality assurance programs.;Chapter 2 presents an analytical solution developed to estimate probabilities of "failure" or advective flux "exceedance" for the case of a geosynthetic clay liner (GCL) situated over a spatially variable composite compacted soil liner (CSL). The risk of utilizing such a liner system is assessed relative to a regulatory compacted clay based soil liner. The analytical solution developed is tested for a range of parameters using the random finite element method (RFEM) and is shown to provide good agreement. The analytical solution is then utilized to examine the "probability of exceedance" for a spatially variable GCL and CSL composite liner system. It is shown that the use of a GCL can potentially result in a low "probability of exceedance" when used with a spatially varying, high hydraulic conductivity CSL. The risk of exceedance generally decreases as the hydraulic conductivity of the CSL decreases. An example problem is presented to demonstrate the capabilities of the analytical solution.